1. Field of the Invention
The present invention relates to an apparatus for and a method of testing whether or not a hollow member of a hollow shape such as a laminated tube, a can, or a can lid has a leakage.
2. Related Art
A member such as the laminated tube or the can may be formed by jointing its parts. The member may also be formed by jointing a plurality of members such as a body and a head piece, or a can body and a can lid. When these members are used as containers, they are required to have a sealing property. It is, therefore, necessary to test whether or not a leakage portion is due to an insufficient joint or due to a defect in the materials, before the containers are filled with their contents. An apparatus for this test is disclosed in JU-A-6-56744 (or JU-B-6-48373).
The apparatus, as disclosed in the Publication, tests the leakage of a gas in a container such as a can. This apparatus is constructed to test the leakage of a container of a sealed structure, by pressuring and injecting a testing gas into the inside of the container, by arranging a gas detecting sensor around the container, and by rotating the container and the gas detecting sensor relative to each other to detect the testing gas leaking to the outer circumference of the container.
However, the above-mentioned apparatus detects the leakage by detecting the gas, as pressurized and injected into the inside of the container, by the gas detecting sensor. Therefore, the gas to be employed cannot but be a gas which is not present in the ambient atmosphere. In short, the apparatus of the prior art has to employ a special gas. Prior to the test, moreover, the gas has to be completely excluded from the atmosphere. For an accurate test without being influenced by the residual gas, therefore, the control process for automation may probably be complicated.
On the other hand, the apparatus of the prior art is constructed such that the testing gas, as pressurized and injected into the container, is blown out from the container and guided into the gas detecting sensor thereby to decide the leakage from the container. When the leakage is restricted or when the testing gas diffuses along the wall face of the container, therefore, it is difficult to capture the testing gas and to guide it into the gas detecting sensor. Thus, it has been difficult to let the prior apparatus have a necessary and sufficient detecting accuracy of leakage.
Since the conventional apparatus detects the leakage by rotating the container, moreover, the spacing between the sensor and the container body is not constant, when the container itself does not have a cylindrical shape, so that the container partially leaves the sensor to make it impossible to detect the leakage at the spaced portion.
On the other hand, the leaking portion or the defect of the container may be a fine pore or a hole, as formed along the face due to the insufficient joint, and the gas flow emanating from such leaking portion will not always be injected outward normal to the container face. However, the conventional apparatus is not equipped with means for guiding the gas positively to the sensor and may fail to detect the gas which leaks from the fine pore or the facial hole so that it is deficient in the accuracy of detecting the leakage. Especially since the conventional apparatus is constructed to rotate the container and the sensor relatively, even with a guard member for guiding the gas near the outer circumference of the container into the detector, a small quantity of gas which leaked from the pore or the hole may flow along the circumferential wall face of the container and may not be accurately detected. These disadvantages become the more serious for the higher relative rotating speeds of the container and the sensor. After all, it is difficult to speed up the leakage test of the container.